Electric noise absorber

ABSTRACT

An electric noise absorber for clamping to a cord of an electronic device comprises a holding case composed of two box-shaped case members. Each case member contains a magnet having a hemi-cylindrical groove at the upper part of the magnet for receiving the cord. It is possible to easily and securely attach and detach the electric noise absorbing magnet to the cord by simply closing and opening the case members.

This application is a continuation of application Serial No. 07/025,059filed Mar. 12, 1987, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to an electric noise absorber for absorbingelectric noise which is generated within an electronic device or whichenters from the outside into the device through a cord.

As a method for absorbing such noise, it is well-known that magneticferrite can be attached to a cord. In this method, two pieces of halfring-shaped ferrite are simply attached by adhesive tape around thecord, therefore, the pieces are apt to easily come off from the cord.Moreover it is troublesome to attach the separate pieces to the cord orto detach the adhesive tape. Furthermore, when a conductive ferrite isemployed, it may make a short circuit or may generate a contactelectricity in the electronic device.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an electric noise absorberin which a magnetic substance can be held securely to a cord for a longtime.

It is another object of this invention to provide an absorber which canbe easily attached to and detached from the cord, whenever required.

It is a further object of this invention to provide an absorber whichcan effectively absorb electric noise and prevent the generation andinflow of noise.

These objects and other related objects are realized by an electricnoise absorber of the invention which includes: two magnetic bodies,each having a hemi-cylindrical groove for receiving the cord; and twocase members for covering the cord when interlocked. Each case membercontains one magnet.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is illustrated diagrammatically in the following drawingswherein:

FIG. 1 is a perspective view illustrating a holding case of the firstembodiment;

FIG. 2 is a plan view of the holding case shown in FIG. 1;

FIG. 3 is a left side view of the holding case shown in FIG. 1;

FIG. 4 is a front view of the holding case shown in FIG. 1;

FIG. 5 is a bottom view of the holding case shown in FIG. 1;

FIG. 6 is a rear view of the holding case shown in FIG. 1;

FIG. 7 is a sectional view taken along line VII--VII of FIG. 2;

FIG. 8 is a sectional view taken along line VIII--VIII of FIG. 2;

FIG. 9 is a sectional view taken along line IX--IX of FIG. 2;

FIG. 10 is a sectional view taken along line X--X of FIG. 2;

FIG. 11 is a perspective view illustrating a ferrite member;

FIG. 12 is a perspective view when an electric noise absorber isattached to a cord;

FIG. 13 is a left side view illustrating the absorber attached to thecord; and

FIG. 14 is a perspective view illustrating a case member of the secondembodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The first embodiment of this invention will be described with referenceto FIGS. 1 through 13.

FIG. 1 shows a perspective view of a holding case 1 of an electric noiseabsorber. The holding case 1 is composed of two case members 2 and 3connected by means of two hinges 4. The case members 2 and 3 arebox-shaped with one open surface and formed so as to securely contain aferrite member 5 shaped as shown in FIG. 11. Four biasing members 6 and7 project resiliently inward from the bottom of the case members 2 and 3for biasing the ferrite member 5. Wide fixing members 8 and 9 areprovided at the center of the front surface (the surface shown in FIGS.4 and 6) of the case members 2 and 3 for securing an upper side of theferrite member 5. Two pairs of flexible supporting projections 10 and 11are formed adjacent to the fixing members 8 and 9. Within the casemember 2, a pair of supporting projections 15 project inward from asurface opposite to the projections 10. Within the case member 3, a pairof supporting projections 16 projects inward from a surface opposite tothe projections 11. The projections 10, 11, 15 and 16 project inwardfrom the front surface so as to support side grooves 5a of the ferritemember 5. Moreover, long engaging tabs 12 are provided adjacent to theprojections 10 of the case member 2. Engaging projections 13 andprotrusions 14 are provided adjacent to the projections 11 of the casemember 3. The projections 13 are engaged with the tabs 12 when theholding case 1 is closed. Substantially semi-circular holes 17 havingteeth 17a are formed on both side walls of the case member 2 forinserting a cord. Likewise, semi-circular holes 18 having teeth 18a areformed on both side walls of the case member 3.

As shown in FIG. 11, a hemi-cylindrical groove 5b is formedlongitudinally along the upper part of the ferrite member 5 forreceiving the cord. The side grooves 5a are formed on both sides of theferrite member 5.

The holding case 1 is integrally formed of a synthetic resin, and eachmember, projection and tab have appropriate resilience.

Two ferrite members 5 are contained in the case members 2 and 3 of theholding case 1. In the case member 2, the upper side of the ferritemember 5 is secured by the fixing member 8. Two pairs of supportingprojections 10 and 15 engage with the side grooves 5a, therefore theferrite member 5 is securely held in the member 2. Likewise, in the casemember 3, the upper side of the ferrite member 5 is secured by thefixing member 9, and two pairs of the projections 11 and 16 engage withthe side grooves 5a. Thus the ferrite member 5 is securely held withinthe case member 3.

In the state that the ferrite members 5 are contained in the casemembers 2 and 3, a cord 30 is inserted between the case members 2 and 3,and the case member 3 covers the case member 2 so that the case 1 isattached to the cord 30 of an electronic device. The engagingprojections 13 of the case member 3 are engaged with the engaging tabs12 of the case member 2, therefore the case 1 is securely fastened. Whenthe case 1 is closed, the biasing members 6 and 7 projecting from thebottom of the case members 2 and 3 support the ferrite members 5 so asto join them together, thereby, the ferrite members 5 are securely held.As shown in FIG. 13, the teeth 17a and 18a, around the semi-holes 17 and18 formed on both side walls of the case members 2 and 3, are clampedagainst the cord 30.

By applying an appropriate number of the holding cases 1 containing theferrite members as the magnetic substance to the cord 30, noise flowingin the cord 30 is absorbed by the ferrite and generation of noise isprevented. The noise absorbing efficiency of the case 1 is measured atvarious positions thereof along the cord by a noise measuring device,and the position for the case where noise is absorbed most efficientlyis found. It is preferable that the most appropriate number of the casesto be used are experimentally determined by measuring the noiseabsorbing efficiency. The ferrite members 5 absorb noise that isgenerated outside or enters the electronic device through the cord.

To detach the case from the cord or to change its position thereon, theengaging tabs 12 of the case member 2 are pulled outwardly so that thetabs 12 detach easily from the engaging projections 13 and the case 1can be opened. It is possible to secure the holding case 1 to a circuitboard with a double-sided adhesive tape.

As shown by a double-dash interrupted line in FIG. 6, a mounting leg 31having an engaging hook may be attached to the bottom of the case member2 or 3 so as to secure the holding case to the circuit board.

Regarding the magnetic substance, either hard or soft ferrite can beused. Further, a plastic magnet or rubber magnet which is made by mixingmagnetic powder of ferrite with plastic or rubber can also be used.

The second embodiment of this invention is shown in FIG. 14. In thisembodiment, an engaging tab 112 and a projection 113 are formed on eachof the sides of a single case member 22. Another projection 113 is alsoprovided opposite to the engaging tab 112. In order to secure the cord30, two same case members 22 are prepared, and one ferrite member 5 iscontained in each case member. Then the cord 30 is held between a pairof case members 22 and the engaging tab 112 is engaged with theprojection 113.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims in the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. An electric noise absorber for surrounding a cordof an electronic device comprising:two bodies of magnetic substance,each having a hemi-cylindrical groove for receiving the cord; two casemembers for covering the cord when interlocked, each case membercontaining one said body; and means for selectively interlocking saidcase members such that said bodies surround said cord, wherein each saidbody has side grooves and each said case member has flexible projectionsfor securing the body in the case member by engaging with the sidegrooves.
 2. The electric noise absorber according to claim 1, whereinthe two case members form halves of one body and are connected by ahinge and each said case member has means for engaging with the othersuch that the case members clamp around the cord.
 3. The electric noiseabsorber according to claim 2, wherein:each said case member isbox-shaped with one open surface; the hinge is formed along alongitudinal edge of the open surface; the engaging means are formed onanother longitudinal edge of the open surface; a semi-hole is formed oneach of narrow edges of the open surface for passing the cord; and teethare formed on an edge of each of the hemi-holes for securing the cordwhen the cases are closed.
 4. The electronic noise absorber according toclaim 3, wherein each said case member has biasing means on a surfaceopposite to the open surface for biasing the body to the cord when thecase members are closed.
 5. The electric noise absorber according toclaim 4, wherein one of the case members has a hook projecting outsideof the case member on the surface opposite to the open surface forsecuring a case to a circuit board.
 6. The electric noise absorberaccording to claim 1, wherein the two case members are formed separatelyand same to each other and said each case member has means for engagingwith each other such that the case members clamp around the cord.
 7. Theelectric noise absorber according to claim 6, wherein:said each casemember is box-shaped with one open surface; the engaging means areformed along a longitudinal edge of the open surface; a hemi-hole isformed on each of narrow edges of the open surface for passing the cord;and teeth are formed on an edge of each of the hemi-holes for securingthe cord when the case members are closed.
 8. The electric noiseabsorber according to claim 7, wherein each said body has side groovesand each case member has flexible projections for securing the body inthe case member by engaging with the side grooves.
 9. The electric noiseabsorber according to claim 8, wherein said each case member has biasingmeans on a surface opposite to the open surface for biasing the body tothe cord when the case members are closed.
 10. The electric noiseabsorber according to claim 9, wherein one of the case members has ahook projecting outside of the case member on the surface opposite tothe open surface for securing the case to a circuit board.